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rs 100 barrel on a rxs100 .. will it work ok?


shambles1980
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Just thinking that a rs100 barrel should just bolt straight on to a rsx?
just need the right piston?

or would i need a con rod change and other dubious ammounts of work?

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  • Moderator

Keep your options open. I have seen dt125/75 mentioned at the same time re gaskets.

Only thing you might need a matching head or it may look a bit wierd.

Did that with my dt 50. An mx big bore with an m head. Wierd but worked well.lol

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its just im not sure about the lengthe of the stroke and stuff..

a rxs bore is 50 approx standard.
and a rs is aprox 52 standard..
So i was thinking it must have less travel.. i know that the combustion chamber on a rxs is prety big for the size of the bore and it can take 52.. so i was thinking the rs may have shorter travel..

the dt is about 1mm to wide to slide in to the bottom end but you can shave some of the casing to mak it fit..

The rs should bolt traight on though.. but i dont see why it has a 52mm standard piston when the rxs would be at the max over sized at 52.

but if it would work, then that would give me a lot of roome to eek more power out.

im not sure the frame can work to well with 175 though, its a really light bike.

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  • Moderator

The important comparisons are window size and height. Primarily the height of the top edge.

And whats known as the deck heights. This is the point that the piston stops at the top and bottom of the stroke.

Finally the length of the piston. You dont want it hitting the crank at the bottom of the stroke.

The actual diameter of the piston in the rs barrel matters not a lot.

I think its ok. I recall a few 100's becoming 125's on the quiet. The rs came as a 125...and a 100cc. Big and i mean kin normous insurance difference between the 2 in the 80's so the 125 died.

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well i found some jusnk out..

the stroke is diferent..
2.0 x 2.0 for the rxs
and 2.0 x 1.8 for the rs..

but the pistons are diferent sizes..

52mm for the rs and 50 for the rxs..
But they are diferent heights too..
50 for the rxs. and 45.6 for the rs

the rs piston wont hit the crank as its shorter,
but the ports would probably end up in the wrong place at the wrong time..
(the piston would travel lower than the barrel is designed for but atleast its not going to smash anything up because it did that)

it looks like it could work.. but really going to end up more work than its worth..

(or am i missing the point entierly)

-edit--

just noticed that its not going to work..

the rxs barrel bolts down to the engine casing. and then has studs for the head. (8 nuts)
the rs uses long studs to hold the barrel and head to the engine. (4 nuts)

or atleast thats what it looks like examening the pictures i found.

so the search continues.

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  • Moderator

C'mon shambles you know you want to.......

http://www.yammy100.com/post85.html

Lookie lookie. Go on.... Rxs175.......devil on your shoulder is hinting.......

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i know.. but i also know that he now has the stock rxs barrel on the bike too..
"dont know why though"

but i managed to snag an rxs100 engine delivered for only 60 notes.
it cant be any worse than my engine and mine is a runner "well kind of lol"..

i may have to mix and match some parts from one to the other but i should be golden now.

the really viable upgrade would be the rx115 cylinder. port it maybe bore it out to +1.00
should be pretty fast then, and i dont think the light frame of the rxs would have any issues with it.
.

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I still think its worth looking at. The dt175 isnt a screamer and the rxs has better manners and brakes than a dt.

That would be a joy to ride. 16hp with the sweet spot at 7000rpm. No hill too high. Aim for top wack flat stick of 75 to 80mph and you would have a cracker.

Play with your old motor a bit. Bet most of the bits you can get cheap on here. Be better than a worked 100. All that torqe.

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im pretty sure i could squeeze out 70 maybe 75 from the 100cc.
would need some tweaks though.
175cc does sound nice thoug seeing as i live 1/2 way up a mountain right now and im moving to 3/4 of the way up the mountain.

even if i dont get much top speed out of it im sure it would get me up hills better.

but im thinking that a 115 cylinder from an rx (all matched up properly) should be 85Mph ish "shouldnt it?"
its just annoying that we dont have them here and would need to be sourced from india or some where like that.

i still dont think id be happy doing 85.. but it would be nice to have 10-15Mph to fall back on if needed.

i have heard that yo can get the 115 to hit a ton.. But i think thats wandering over in to the realms of "a bit far fetched"
although i guess with good porting and everything like new.. and if you only wieghd 6 stone.. with the wind behind you.. going down hill... It could maybe do it But i dont think so..

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I remember a truly hideous red and yellow rxs from the dark ages that absoloutly flew.

Looked like a reject from bollywood but god it was fast. Maybe that was done like that......

I would do it just to see if i could. I still have a hankering to lc the dt. Or with more finantial permission. See if a rd200 will go.

Get the purists wound up....

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il see if i cant find a 115 barrel head and piston some where but i dont think i will. i had a hard enough time getting the 100 lol.
i just dont see the rxs doing 100mph with 4 gears.. the rx 115 has 5 i think..

but i guess if you messed with the teeth you could tune it up for flat out speed. but i dont think thats a good option,

il probably just get this running sweet and thrash it for a while.
then set my eyes for a tzr 125 or an ar 125. the ar would have to have a full disk valve though. just that alone makes a huge diference. But lots of that bike needs tweaking to get it from the stupid uk restricted junk to the full on AR125 expieience...
the tzr dont need much messing with though. but i have a soft spot for the ar125.

my 1st bike "that wasnt a c90/rev n go/peddal/pump to start chicken chaser" was an ar125..

looked abit like this
Kawasaki-AR_125-1982.jpg

bought it for £70. then sold it on.
now i cant find one :(

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I remember them. Fast if you could afford/wangle de restricting them.

Made them unpopular as the yam came and whupped it in the easy fast category.

Like a baby 900r

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really happy with the engine i recived today.
A bit duious about why the serial number had been hammerd in to oblivion.. But decided what the heck. il just take the barrel off and use it on mine..

just to make sure i sealed up where the reed valve goes to the inlet on my piece of junk barrel using instant gasket.,.
and sure enough it works better.. So i tore round the garden some..
Its been snowing so i had fun spinning the back end around the obsticles.
Still not running sweet or anythging but i was able to thrash it around the garden a bit..

went ahead and took the barrel off the new engine..
Decided that as the engine number was already hammerd to pieces id get the barrel off by undoping the nuts then using a teenye tiny smashing motion with a hammer aimed right at the engine numbers..

that made the barrel come off nice and easy.

had a look and it looks in good condition.
grabbed the calipers and its at standard bore size.
the piston also looks in good condition as do the rings.

think il just slap it on as it is "probably go and get new rings though" and 90% of the issues should be gone away.

Happy days.

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Jammy bugger.

Still not tempted to protortype the 'warmer' engine....

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i may see what can be done with the now barrel less new engine..
but i need to get my engine out and in bits asap now. so i can do the rebuild.
im happy to be using the original engine though as numbers all match up.

i did all my detective work now. prety sure i have found every issue it had.
nice new bearing all round. nice new seals and gaskets.
everything torqued up properly. and il then see if theres something wrong woith the cdi "already have a spare just in case"
i dont think the cdi is bad though. i really do believe all the issues this bike had came from some one with ham fists using a bar on a spanner.

i have shiney new stainless engine bolts to to go back in when im puting it back together. il have to resist the temptation to just throw it together and jam it back in the bike, because i really want to sand the frame down and paint it with hammerite,
im also going to send the pannels and tank off yo a friend to get painted properly.
Im still thinking british racing green.. im not a huge fan of the stock red/blue.. black is an option. the guy can do pearlesent ?.. It changes colour as you look at it..
But i think thats a bit vain, so probably just a solid colour. And maybe some pin striping.

the costs are starting to rack up if im honest, but it shouldnt be long before its road legal now.

Still have stupid little things to get though.
ignition barrel with key and petrol cap with key. (both of mine have been attacked with a screw driver, but apparantly not very well as only the key will start it)
and i need wing mirrors.
the seat is more than likley salvagable from what ive read. and the seat cover is in decent condition..
oh and il probably just buy a new rear indecator stalk and all.

but apart from that.. and the fresh oil for forks, gearbox and 2stroke..
its just wating to get done.

And we should be moving up there in the next week or so, as im prety much done working on the actuall house..
so i can have a few late nights tinkering.

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  • 2 weeks later...
  • Moderator

there is another engine on Gumtree ATM in Manchester £45

http://www.gumtree.com/p/cars-vans-motorbikes/rxs-100-complete-engine-carb-exhaust-manchester-45/1008109956

he's about 2 miles from where I live so may have other bits too

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